Magnetic door latch



April 18, 1957 w. H. VAN DONSELAAR 3,314,707

MAGNETIC DOOR LATCH Filed July 14, 1965 INVENTO'R. WIL HEL MUS H.VAN DONSE'LAAR AGENT 3,314,707 MAGNETIC DOOR LATCH Wilhelmus Hendrickus van Donselaar, Emmasingel, Eindhoven, Netherlands, assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed July 14, 1965, Ser. No. 471,853 V Claims priority, application Netherlands, July 29, 1964,

Claims. (Cl. 292-2515) The invention relates to a magnetic latch for a door and the like comprising a bolt which cooperates magnetically with a keeper. The bolt is slideably arranged in a tiltable guide, the bolt and the keeper being separated from one another by tilting of the guide. A blocking mechanism which prevents tilting of the guide is coupled to a door knob shaft which is pushed or pulled in the direc tion of door opening movement, the blocking mechanism being removed by pulling or pushing the knob.

In such a magnetic latching, the bolt is slideably arranged in the guide so that magnetic attraction extends or retracts the bolt automatically relative to the tilting guide. Since the bolt is extended when the guide tilts, it is necessary that the hole in the cover plate is much wider than the width of the bolt. As a result of this, dirt can enter through the aperture in the cover plate as a result of which the locking device will operate less satisfactorily in time.

The invention over-comes this problem since the guide is arranged rotatably within a housing and the axis of rotation of the guide extends parallel to the tilt axis of the bolt. Also the bolt lies inside the rotatable guide and only a slight amount of plate exists so that dust and the like are substantially excluded.

An object of the invention is to provide a magnetic latch having a pushepull knob releasing mechanism.

Another object of the invention is to provide a latch in which the bolt is entirely retracted when the door is open.

Another object of the invention is to provide a magnetic latch in which the bolt extends and retracts solely under the influence of magnetic attraction.

The drawing shows a perspective view of a magnetic latch according to the invention partially broken away and in which the parts are shown in the rest position.

This magnetic latch, a so-called push-pull latch, consists of a metal housing 1 having a brass cover plate 2 in which a rectangular aperture 3 is provided. The magnetic bolt 4 is slideable within a bronze guide 5. The magnetic bolt 4 consists of a sandwich composed of a flat oxide ceramic permanent magnet 6 of Ferroxdure, between two soft iron pole plates 7 and 8. The magnetic bolt 4 can move substantially without friction relative to the guide 5. When attracted by a keeper, the bolt emerges from the guide 5 and projects through the aperture 3 in plate 2. The distance the bolt projects outwardly beyond the cover plate is determined by a stop member 11 which is secured to the pole plate 8, and a small adjusting screw (not visible in the drawing) provided on the front of the guide 5 extending into a threaded bore in the side 10. The stop 11 moves within the slot 9 within which the end of said screw projects. The guide 5 is suspended in the casing 1 by pivots 12 and 13 and can therefore rotate in a restricted are. In the rest position, the guide 5 engages that side of the casing which is located opposite to the points 12 and 13 (i.e. the side 31). The magnetic lock further comprises a blocking mechanism for the guide. This blocking mechanism comprises a nylon pawl 14, which has a triangular cross section and rotates around the shaft 15 at its apex, and of a coupling arm 16 which is also rotatably connected to the shaft 15 and pawl 14 via the levers 17 and 18. The shaft 15 sup- United States Patent 0 ports a helical spring 19 one end of which is threaded in a hole in the pawl 14, as indicated in the drawing, and the other end 20 loops over the coupling arm 16. A brass sleeve 21 is attached to the inner end of the guide 5 so that it lies behind the pawl 14 in the rest position. Two upright studs 22, form abutment members against which the pawl 14 is held by the spring 19. In the rest position, the coupling arm 16 abuts the wall 31 of the casing 1 against which the guide 5 is also held by magnetic attraction. The coupling arm 16 has an elongated hole 23 which corresponds to two oppositely located holes (not shown) in the walls of the casing 1 through which extends the operating shaft 24 in the of the lock. This shaft 24 is provided with two abutment sleeves 25A and 25B each of which are normally spaced a distance from the coupling arm 16. The shaft 24 is provided at each end with a door knob 27 and can move the coupling arm 16 out of its rest position when a knob is pushed in the direction opening the door or pulled in this direction. A helical spring 26 surrounding sleeve 25B serves for returning the shaft 24 to its initial position. The magnetic latch further comprises a soft iron keeper 28 having a wedge shaped rise 29 and a recess 30. When the latch is mounted in a door, the keeper is attached to the door jamb by means of, for example, wood screws.

At the beginning of the latching operation, all the parts of the latch are in the rest position. A door which is provided with this push-pull latch may be closed without operating the knob. As soon as the bolt 4 and the keeper approach one another, the bolt 4 begins to move out of the guide 5 in the direction of the keeper 28. At a given instant the pole plate 7 of the bolt 4 engages, under a very small force, against the wedge-shaped rise 29, and slides in the latching direction along the rise until it enters the recess 30 of the keeper. The door is now stopped by the rectangular side of the keeper since the guide 5 abuts the side 31 of housing 1. When the contacting surface of the pole plate 7 is rounded the bolt slides along the rise of keeper 28 in a particularly smooth operation. For opening the door, the appropriate knob is pulled or pushed, as a result of which the coupling arm 16 is moved out of its initial position while simultaneously a force is exerted on the door in the direction for opening. Movement of the coupling arm 16 rotates the pawl 14 so that the guide 5, hinged at points 12 and 13, is no longer held against rotation by the pawl. The force exerted on the door now causes the guide to rotate as the door moves in the direction of the opening. The bolt 4 in the guide 5 will first tilt a little on the keeper 28 around the wedge-shaped rise 29. This strongly reduces the magnetic attraction (on the order of magnitude 10 kg.), since the bolt is inclined as a result of the tilting and side 8 of the bolt readily slides over the rise 29 of the keeper 28. When the door is further opened the bolt 4 is separated from the keeper and the bolt 4 is automatically retracted into guide 5 by magnetic action, whether the knob 27 has or has not been released. The guide 5, which is still tilted, will return to its initial position as a result of the attraction between the bolt 4 and the iron Wall 31 of the casing. The brass sleeve 21 then passes the pawl 14 if the knob has not yet been released.

If the knob has been released before the guide rotates to its rest position, the brass sleeve 21 engages the pawl 14 and by virtue of the leverage provided by properly dimensioning the appropriate parts the force of spring 19, holding the arm 16 against wall 31, is overcome and the sleeve 21 slips behind the pawl into its blocked position.

It 'will be apparent that a door provided with the latch described cannot be pushed open from its closed position because such a force is transmitted via the bolt 4 to the guide 5, but the guide 5 cannot rotate because the pawl assembled condition 14 only urges the arm 16 housing 1.

While I have shown and described the preferred embodiment of my invention, it will be understood that the latter may be embodied otherwise than as herein specifically illustrated or described and that in the illustrated embodiment certain changes in the details of construction and in the arrangement of parts may be :made without departing from the underlying idea or principle of the invention within the scope of the appended claims.

What is claimed to be new and useful and secured by Letters Patent of the United States is:

1. A latch for a door comprising in combination with a housing, a bolt of permanent magnet material, guide means supporting said bolt for free relative sliding movement, means pivotally supporting said guide means for rotation about an axis substantially normal to the sliding axis of said bolt, door knob :means and means operatively connected with said door knob means for holding said guide means against pivotal movement and releasing said guide means; and a soft iron keeper for engaging said bolt.

2. A latch according to claim 1, wherein said means operatively connected with said door knob means comprises a pawl member having an integral coupling lever, means for pivotally supporting said pawl member for movement from a position engaging said guide means to a position remote from said guide means, spring means for biasing said pawl member and coupling lever into said blocking position, and means connecting said coupling lever with said door knob means.

3. A latch according to claim 2 wherein said pawl member is of a generally triangular shape, and said means for pivoting said pawl member being connected thereto at the apex of the triangle.

4. A latch according to claim 3 wherein said housing against the Wall 31 of the comprises a soft iron portion located relative to said guide member a distance equal to approximately three quarters of the length of said bolt for attracting said bolt and guide.

5. A latch for a door comprising in combination, a hollow guide member of non-magnetic material, a bolt of permanent magnetic material receivable within said guide member for sliding movement relative thereto, means for pivotally mounting said guide member, a triangular pawl member for blocking pivotal movement of said guide member in a first position thereof, means for pivotally supporting said pawl member at the apex thereof and biasing said pawl member to its blocking position, a knob and associated means, means coupling said pawl member and said knob means for moving said pawl out of said blocking position, and a latch housing member having a soft iron portion positioned relative to said guide member for returning said guide to said first position by magnetic attraction between said bolt and said soft iron portion.

References Cited by the Examiner UNITED STATES PATENTS 605,170 6/1898 Meigs 292-63 2,097,232 10/ 1937 Hartman 292-192 X 2,696,398 12/1954 Teetor 292-71 X 2,736,702 3/1957 Teetor 292-2515 2,970,857 2/1961 Squire 292-2515 3,129,968 4/1964 Graham 292-2515 X FOREIGN PATENTS 1,266,060 5/1961 France.

EDWARD C. ALLEN, Primary Examiner.

R. E. MOORE, Assistant Examiner. 

1. A LATCH FOR A DOOR COMPRISING IN COMBINATION WITH A HOUSING, A BOLT OF PERMANENT MAGNET MATERIAL, GUIDE MEANS SUPPORTING SAID BOLT FOR FREE RELATIVE SLIDING MOVEMENT, MEANS PIVOTALLY SUPPORTING SAID GUIDE MEANS FOR ROTATION ABOUT AN AXIS SUBSTANTIALLY NORMAL TO THE SLIDING AXIS OF SAID BOLT, DOOR KNOB MEANS AND MEANS OPERATIVELY CONNECTED WITH SAID DOOR KNOB MEANS FOR HOLDING SAID GUIDE MEANS AGAINST PIVOTAL MOVEMENT AND RELEASING SAID GUIDE MEANS; AND A SOFT IRON KEEPER FOR ENGAGING SAID BOLT. 